(i) Field of the Invention
The present invention relates to a magenta dyestuff for sublimation transfer recording.
A heat transfer system using a sublimable dyestuff is a printing system in which a thin condenser paper having a thickness of several microns or a PET film is coated with the sublimable dyestuff in the state of an ink, and this dyestuff is then selectively heated with a heat-sensitive head to transfer an image to the recording paper. In these days, this heat transfer system has been used as a means for recording (hardcopying) various information images.
The sublimable dyestuff used herein is characterized by being rich in colors, excellent in color-mixing properties, and having strong dye-fixing power and relatively high stability. Accordingly, the above-mentioned heat transfer system using this kind of sublimable dyestuff has an important feature that the amount of the dyestuff to be sublimed depends upon heat energy and the density of the fixed dyestuff can be analogically controlled. This feature is not present in other image-recording systems.
Most of azo dyestuffs which have been heretofore suggested (Japanese Patent Application Laid-open No. 61-227092) usually have high molar extinction coefficients and latently possess transfer power necessary to obtain the sufficient density of transferred images. However, on the other hand, they have insufficient solubility and poor compatibility with ribbon binders, and thus these dyestuffs tend to crystallize on ribbons, so that the heat transfer efficiency of the dyestuffs is noticeably impaired. Furthermore, after the transfer, when brought into contact with the dyestuffs, matters are soiled therewith and the quality of the images themselves deteriorates because of the poor dye-fixing power of the dyestuffs. In addition, since most of these dyestuffs are poor in durability, particularly light resistance which is most important, they cannot withstand a long-term storage. Hence, the dyestuffs which can solve all of these problems are extremely limited.